Question

Which of the following is not a gaseous fuel?
A) CNG
B) Coal gas and water gas
C) Gobar gas and acetylene
D) Liquid hydrogen

Answer 1

Hint: we know that hydrogen is naturally in gaseous state but as a fuel we uses a fuel in liquid state named liquid hydrogen, it is represented by $L{{H}_{2}}$, While its chemical formula is ${{H}_{2}}$.

Complete step by step solution: If we go through option to option we have check states of all the given options,

CNG: Compressed natural gas, it is the methane that is stored at high pressure, and used in a substitute of gasoline, and diesel because of its cheap cost.

Coal gas: A mixture of gases (chiefly hydrogen \[{{H}_{2}}\], methane$C{{H}_{4}}$, and carbon monoxide $CO$) obtained by the destructive distillation of coal and formerly used for lighting and heating.

Water gas: A fuel gas consisting mainly of carbon monoxide$CO$ and hydrogen \[{{H}_{2}}\], made by passing steam over incandescent coke.

Gobar gas: In India, biogas is commonly known as gobar gas. Because it is prepared by decomposition of organic matter, and in India cow dung in Hindi is called gobar. It’s main component is methane gas $C{{H}_{4}}$.
Acetylene${{C}_{2}}{{H}_{4}}$: it is also in gaseous form used as a fuel.

Liquid hydrogen: To exist as a liquid, \[{{H}_{2}}\]must be cooled below its critical point of \[33~K\]. However, for it to be in a fully liquid state at atmospheric pressure, \[{{H}_{2}}\] needs to be cooled to \[20.28~K\]. One common method of obtaining liquid hydrogen involves a compressor resembling a jet engine in both appearance and principle. Liquid hydrogen is typically used as a concentrated form of hydrogen storage.

Additional Information: Liquid hydrogen is a common LIQUID ROCKET FUEL for rocketry applications, The product of its combustion with oxygen alone is water vapour (although if its combustion is with oxygen and nitrogen it can form toxic chemicals), which can be cooled with some of the liquid hydrogen. Since water is often considered harmless to the environment, an engine burning it can be considered "zero emissions". In aviation, however, water vapour emitted in the atmosphere contributes to global warming (to a lesser extent than $C{{O}_{2}}$). Liquid hydrogen also has a much higher specific energy than gasoline, natural gas, or diesel.

Note: For solving these types of questions we have learned the chemical formulae of these fuels.and learn the components of gobar gas, coal gas, water gas, and CNG.